Combination distillation and liquation furnace



Nov. 17, 1936. M. F.APERK1Ns 2,051,250

` COMBINATION DISTILLATION AND LIQUATION FURNACE Filed Aug. 5, 1932 2 Sheets-Sheet 1 w w//W//y K gj@ ATTORNEYS Nov. 17, 193s.

2 Sheets-Sheet 2 M. F. PERKINS Filed Aug. 5, 1932 COMBINATION DISTILLATION AND LIQUATION FURNACE INVENTOR Blfv/vI/e ffl/911s M 4 Qa;

ATTORNEYS l Patented 'Nom 17, i936 mirar autres@ erica CGNBINATION DSTmTlION AND LIQUATION FURNACE rApplicationAugust 5, 1932, Serial No. 627,589 1o claims. (ci. 26e-11) 'Ihis invention relates to the separation and/or purification of substances by liquation and distillation. The inventionparticularly relates to apparatus for treating zinc contaminated with lead for the production of zinc vapor in a substantially pure form while simultaneously eecting a concentration of the lead.

'I'he method disclosed herein is claimed in my application Serial No. 736,895, led July 25, 1934.

The invention provides apparatus for continuously and simultaneously subjecting impure spelter to the processes of distillation and liquation in such manner that zinc is continuously distilled from a bath whose low lead content is maintained at a low value by continuous liquation. The invention further provides a. furnace having two chambers or compartments connected by appropriate passageways for effecting an intercirculation of molten metal between the compartments, which makes it possible to practise continuous distillation in one compartment while continuously subjecting the metal in the other 4.compartment to liquation.

. to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may. be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 is a cross section of a furnace embodying the principles of the invention; and

Fig. 2 is aplan view in section of the same furnace on the line 2-2 of Fig. 1.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in theirapplicationf'as the art will permit.

Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosures of the invention are made for purposes of explanation, but it will be understood that the details may be modied in various respects without departure from the bro'ad aspect of the invention.

Referring now to the drawings, a furnace is shown having walls I0, II, I2, and I3, roof I4 and hearth I5, the latter resting on base material I6. Insulation Il is provided to cover the roof and walls.

A common wall I8 extending from the roof to the hearth divides the interior of thefurnace into two chambers or compartments I9 and 2U which are connected by ports or passageways 2I and 22 extending through wall I8. 23 of suitable refractory material extend through walls I2 and I3 and chamber 20. Passageway 24 connects flue 26 with chamber I9 through port 25. Chamber I 9 is provided with a charging port 21 and tap hole 28, while chambers I9 and 20 are provided with exits 29 and 30 respectively. -A safety Vtrap 3l is provided in the lower portion of flue 26 by dam 32. Suitable doors not shown are provided for cleaning compartments I9 and 20.

In operation, the invention may be practised as follows. The furnace is charged with the material to be treated and the furnace heated to the proper temperature. For the recovery of zinc from lead, typical substances which may form the charge are raw spelter, galvanizers dross, zinc dross, leady zinc, salvage materials of a similar nature and the like. It is generally preferable to introduce the charge into the liquation compartment through charging port 2l, although special cases may warrant direct charging to the distillation chamber. Again, the charge may be introduced either in the liquid or solid state, depending upon circumstances.

Fire tubes After melting the charge in the furnace, the

respective baths of the liquation and distillation compartments are brought to their appropriate temperatures. The temperature in the liquation compartment is maintained at a value slightly above the melting point of the bath, while in the distillation compartment a sufficient temperature is maintained to insure rapid volatilization of zinc. In general, it has been found that a temperature range of from 430 C. to 500 C. is appropriate for the liquation compartment, while operation of the distillation compartment at temperatures slightly above 900 C. gives excellent results.

Heat may be supplied to the distillation compartment by means of submerged fire tubes constructed of carborundum, graphite, or similar material and which are fired internally with an air-fuel mixture employing the principles of surface combustion. If desired, the re tubes may be anchored for increased mechanical strength, as by embedding same in the furnace hearth. Other heating means may be employed, but those in which the heat is supplied below the free surface of the bath are preferable.

` A portion or all of the hot gaseous products of combustion from the lire tubes 23 may be conducted through passageway 2d and into the liquation compartment through port 25 to com.

plete the heat balance in that compartment of the furnace. Combustion gases not used for this purpose are vented through flue 2E.

To provide intercirculationand exchange between the liquation and distillation compart-l ments suitable ports 2l and 22 are provided in the dividing wall I8. The rate of circulation may be controlled by the number, size and location of these connecting ports, thus eliminating any necessity for employinga pumping scheme or other- Hence, in operation, yzinc vapor substantially free from lead is volatilized 'and removed from the compartment through exit 30 from whence it may be condensed to form high grade zinc metal,

burned to produce zinc oxide, or otherwise utilized.

\ Unlike ordinary distillation practices in which the ratio of lead to zinc in the bath must necessarily increase as volatilization of the zinc progresses, the present invention continuously maintains a low ratio of lead to zinc in the bath undergoing distillation. The maintenance of this low lead value is made possible by the intercircu` lation and exchange eiected between the distillation and liquation compartments. As a result of this circulation, the lead left behind in the distillation compartment following the volatilization of the zinc is circulated into the liquation compartment which, as before stated, is substantially cooler than the distillation compartment: At this lower temperature, the lead is less soluble in the zinc and, hence, separates out as a liquid which collects at the bottom of the compartment because of its higher specic gravity.

As the zinc content in thev furnace is decreased by volatilization and the lead concentrated in the bottom of the liquation chamber, additional charges of material may be added to the system without interrupting the continuous operation of the furnace. As before stated, the charge may be liquid or solid and may be charged to either compartment, although it willV normally be introduced into the liquation compartment. As lead accumulates in the liquation compartment, it may be removed at convenient intervals via top hole 28. I

In order to more clearly illustrate the advantages of the present invention and its mode of operation, the following specific example is set forth. Zinc containing from 6% to 10% lead with a trace of iron was charged to the furnace.

The liquation compartment was maintained at from 450 C. to 500 C., while the distillation compartment was operated slightly in excess of 900 C., at which temperature volatilization of the zinc proceeded rapidly. Samples of the metal taken from the distillation compartment and the upper stratum of the liquation chamber analyzed 3.06% lead and 3.00%, lead, respectively. At the same time, a sample taken from the bottom of the liquation chamber analyzed 96.3% lead, while the volatilized zinc emerging from the distilla- -tion compartment analyzed less than .003% lead.

As previously stated, it is possible by the present invention to continuously distillzinc vapor from a bath of low lead content and the above example illustrates this fact. The importance of constantly maintaining the lead content of the bath in the distillation compartment at a low value, which is made possible by the present invention, is forcibly presented by the following results obtained in making several ordinary distillations from a bottle-shaped retort and employing a small vapor phase filter. of crushed rock to prevent splashes of lead in the retort reaching the condensate:

Analysis of melt Analysis of the distilled in the retort and condensed zinc Lead by weight Lead by weight 2 less than 0. 001 3 0. 003 5 0. 01 0. 012 0. 02 0. 03

This table clearly illustrates the well known fact that as the percentage of lead in a bath from which Zinc is being volatilized is increased, the percentage of lead in the vapor and condensate is also increased. By means heretofore described,

, the present invention, at all times, insures a low `liquation chamber for melting material charged in the solid state.

Again, while the invention has been described with reference to the separation of lead and zinc, it will be appreciated that the apparatus of the invention may be used to advantage in effecting a large number of separations wherein the appearance of a new phase is produced by change of thermodynamic environment.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be madeby those skilled in the art without depa ing from the spirit of the invention.

What is claimed is:

1. An apparatus for continuously effecting a separation between zinc and lead by simultaneous distillation and liquation which comprises an insulated furnace having liquation and distillation compartments, a wall common to said compartments, passageways through said wall at least one of same being at the hearth level of the furnace, fire tubes positioned in said distillation compartment and means for conducting waste gas from said re tubes to said liquation compartment.

2. In the separation of zinc from lead, a furnace having liquation and distillation compartments, means for effecting intercirculation and exchange of molten metal between said compartments, means for heating said distillation compartment and means for conducting waste heat therefrom to said liquation compartment.

3. In apparatus for the separation of lead and zinc, the combination of a liquation chamber, a distillation chamber, sub-surface heating means for said distillation chamber and means for interclrculating metal between said liquation and distillation chambers.

4. A furnace for effecting a separation between zinc and lead comprising a liquation chamber, a distillation chamber, a hearth common to Aboth of said chambers, means for maintaining a proper-heat balance in said chambers and means for effecting intercirculation and exchange of molten metal between said chambers, said means comprising passageways communicating between' said liquation and distillation chambers in different horizontal and vertical planes.

5. A furnace comprising a liquation chamber, a distillation chamber, sub-surface heating means in said distillation chamber and means enabling i a thermo-Siphonic circulation of material between said compartments.

6. A metallurgical furnace comprising the combination with a. roof and hearth, of a Wall extending from the roof to the hearth and dividing the interior o f the furnace into two compartments, means for circulating metal from each compartment to the other compartment comprising ports in said Wall spaced both horizontally and vertically and heating means disposed to deliver heat to the metal in at least one of said compartments below the free surface of the bath.

7. A metallurgical furnace comprising the combination with a` roof and hearth, of a wall extending from the roof to the hearth and interiorly dividing the furnace into a pair of compartments, means extending through the said wall for effecting yintercirculation and exchange ofvmolten metal between said compartments, re tubes in one of the compartments for effecting a direct heating thereof and means for conducting hot gases from the lre tubes to the other compartment.

8. A metallurgical furnace comprising the combination with a roof and hearth, of a wall extending from the roof to the hearth and interiorly dividing the furnace into two compartments said wall being provided with passageways enabling intercirculation and exchange of molten metal between said compartments, means'for indirectly heating one of the said compartments and a duct leading from said compartment to the other compartment for conducting hot gases from the indirectly heated compartment for heating the other compartment.

9. A metallurgical furnace comprising the combination with a roof and hearth of awall extending from the roof to the hearth and interiorly dividing the furnace into a pair of compartments, means extending through the said wall for effecting intercirculation and exchange of molten metal between the compartments, means for indirectly heating one of the said compartments, a ue communicating with the indirectly heated compartment and means interconnecting the flue and other compartment for conveying hot gases from the ue to the other compartment for heating the latter.

10. A metal treating furnace comprising two compartments, means for heating metal in one of said compartments by applying heat thereto below its free surface, and means for effecting thermosyphonic circulation of metal between said compartments, said means comprising passageways interconnecting the compartments and spaced both horizontally and vertically.

M'ELVILLE F. PERHNS. 

